THE HISTORY AHD CONSTRUCTION
OF THS
POTOMAC DAM
MS
GREAT FAILS, MARYIAHD
BY
CONSTANT INS E. LOZUPONS
+/27/34
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THE HISTORY AND CONSTHUCTION OF THE POTOMAC DAM AT
GREAT FAIIS^MAHYLAND
The romamce of the Great Falls of the Potomac embraces
more thaa three eeaturles of American history. This spot of
scemlc sple»dor, water supply, aad poteittial power has lomg
beem a coveted prize, aftd title to the falls has beam a
comstamt source of dispute. The earliest record of the falls
is ia the gramt of Marylamd lamd to Lord Baltimore by Charles
the First im 163S, The graat of the lamd imcluded the Potomac
River of which the Great Falls are a part, im 1688 the gramt
of Tirgimia lamd to Lord Culpeper by James II also imcluded
the Potomac River.
The real history of Great Falls begims with the close
of the Hevolutiomary War whem Tirgimia gramt ed a charter to
the '*Potowmaek Compamy" givimg it exclusive aavigable rights
to the river. The presldemt of this compamy was George
Washimgtom, The "Potowraack Compamy" built five eamals mear
the falls but mever accomplished amythimg defimite Im the
lime of mavigatiom*
Om Jamuary £7,1824 the virglmia legislature revoked the
charter of the "Potowmaek Compamy" amd gramted a mew ome to
the Chesapeake amd Ohio Carnal Compamy, This charter provided
that the water of the Potomac should forever be reserved to
maimtaim the compamy 's carnal. The compamy had first rights
to the river. The water which the carnal compamy did mot re-
quire for mavigatiom purposes could be used by the govermmemt
Great Falls of the Potomac, Maryland, 15 miles from WashlnBton, D. C.
1
Government [Vd n, Careat Falls of the Potomac, Maryland, 15 miles from Washington, D, C,
The X'6 mark +he bouncloflet» o-f +Ue cl«t^
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or other emterprlses. The peculiar thimg about the charter was
that virglmia had mo jurisdictiom over the Potomac amd hemce
oo-uld mot give amy compamy rights to the river » Owmership of
the river was defimitely settled betweem liarylamd amd Virgimla
by agreememt. The gramt of torylamd lamd by Charles I im 1632
to Lord Baltimore was held superior to the later gramt of
Virglmia lamd by James II to Lord Culpeper. It was defimitely
deteraimed that the Potomac River is part of the state of
Marylamd, the state lime beimg low -water mark om the Tirgimia
side.
But the fact that Virgimia im reality did mot have Juris-
dictiom over the Potomac mever bothered the Chesapeake amd
Ohio Camal Compamy. This eomcerm wemt over iato Marylamd amd
om Jamuary 31,1825 had its Virgimla charter approved by the
Old lime State, Later it had its charter approved by Pemasylvamia
amd om K'lay 3,1825 had the agreememt to which three states amd
the camal compamy were parties, approved by act of comgress.
This is where the carnal compamy gets its perpetual rights to
the Potomac. Its charter has be em held by the Supreme Court
to be am agreememt betweem states which the Comstitutiom
protects from impairmemt. No power save am ememy who might
oomciuer the matiom cam take that right av^/ay from the compamy.
Fortumately there has beem amd still is suffioiemt water to
rum the camal amd supply the District of Columbia as well.
The mext eomcerm imterested im the Potomac was the Great
Balls Mamufacturimg Compamy, This corporatiom was chartered
by Virgiflia om February 4,1639, It acquired about 750 acres
of lamd om the Virglmia side of the river, just below the
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falls a»d also about 61 acres of Coma's Island im the river,
beimg the islamd across whose southern point the present dan
exteads, Oa April 2, 1895 the Great Falls J/Iaaufactiiriag Co.
sold Its fraachises, rights, aad real estate to the Great
Falls Power Coapaay which had beea chartered by Virgimia ia
1894, Neither of these oompaaies accomplished aaythiag, their
sole object seemiag to be holdiag the laad -uatil the goTerameat
would aeed it for water works aad thea demaad aa exorbitaat
price for it.
ia 1853 the IJaited States first attempted to use the
water of the Potomac by acquiriag iaterests at Great Falls,
It obtaiaed the coaseat of Marylaad to tap the river for water
supply that year, aad decided to use the lower ead of Coaa's
Islaad for a dam exteading from the Maryland shore. At this
time the Great Falls Maaufacturiag Compaay did aot owa Coaa's
Islaad. It purchased the Islaad ia 1854 aad whea the goverameat
started to put its water supply plaa iato operatioa it had to
settle with the maaufaeturing eompaay, A jury assessed the
daaages at $150,000, The award was atrocious whea it is coa-
sidered that the Uaited States bought 130 acres about the falls
for oaly $3,720, The laad ia quest ioa was a sn^ll strip across
a sterile islaad 600 feet wide, it is sigalfieaat that from
1839 to 1853 the compaay had displayed mo sigas of actirity.
As sooa as the goverameat begaa making plans for use of the
river for water supply, the maaufaeturing compaay got busy
buyiag Coaa's Island aad demaadiag aa exorbitaat price for the
part of it the Uaited States had to have. The government refused
to accept the award of the jury and for aeariy ten years the
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oase was im litigatio*. Fi»ally, ia 1862, by agreemaiit, It
was t-uraed orer to a oommissioa of fire lawyers, who rec-
oameaded several plaas oae of whicti Involred tlie paymeat of
$15,692 aad gave the goverameat the right to build a dam at
Great Falls. The maaufactttriag compaay refused to accept the
decisloa, but the Uaited States weat ahead aad built the daa
aayway, completing it ia 1867, The compaay sued for $500,000
ia the Court of Claims aad la 1880 was giTea ^15,692, the
e^Act amount of the award uader the plaa of the connlssioa.
The maaufacturiag oontpaay appealed this case to the Supreme
Court of the uaited States aad lost. The plaa adopted gave
the Uaited States the right to build a dam across the ^larylaad
Chaaael to Coan's islead, aad gave it the use of all the water
the daa diverted, Prom 12,000,000 to 24,000,000 galloas per day
were used from the time the dam was completed la 1867 uatil
1882 whea it was proposed that the Uaited ^states acquire add-
itioaal water rights at Great flails to iacrease the water supply
of fMshiagtoa.
Ia 1882 Coagress passed a bill providiag for the acquisitioa
by coademaatioa of sufficient laad to extead the dam from Conn's
Island to the Virgiaia shore. The maaufacturiag compaay again
put ia a big claim and tried to stop the work. The exteaded dam
was completed ia 1886, but ia the meaatime, the maaufactiiriag
compaay had filed a claim for $1,000,000, This was a soxirce of
coatroversy for tweaty years aad was pressed by the Great Palls
Power uompaay after that coacera took over the property aad
fraachises of the maaufacturiag company ia 1895, This claim
was fiaally settled ia 1902, the uaited States payiag damages
of $63,766, The total sum which the governmeat has paid for
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water priTileges at Great i-'alls, exclTisiye of its purchases of
real estate, is as follows:
Arbitratlo* iacpeases $ 12,761.84
Great ifalla Aamufactxirlag Co. 15,69 2.00
Great Fails I'ower Co. 63.766.00
Total $ 92,219,84
These paymemts, it must be co&sidered, were to eomcerms that
had meTer dome aay of the thimgs for which they were ia corpora ted;
that had Mever developed am o\mee of Great rails power diiriEg
sevemty years of life; that had never performed a single public
service. Yet whe» the govermmeMt wanted to utilize some of the
water it had to pay them nearly $ 100,000,
Previous to December 3, 1863 the aoiirce of water for the
District of Col-ombia came from wells aad springs, very early it
became apparent that such a supply would not be adeqiiate for the
rapidly growing oity in coming years. Studies were therefore made
of possibilities of using the Potomac River as a source of water.
Surveys to ascertain the best method of supplying water to the
city of Washington were ordered by President Pillmora. In February
1853, the report of Captain M.C.Meigs, who had been assigned to
this work, was forwarded to Congress by President Killmore, The
report recommended a gravity supply from the Great Falls of the
Potomac some fifteen miles above "/Washington, by a conduit nine
feet in diameter, capable of delivering more than 67,000,000
gallons per day. The population of Washington at that time was
about 50,000 and of Georgetown, now west Washington, about 8,000.
At that time Boston had a supply of 10,000,000 gallons per day.
New York of 30,000,000, and Philadelphia of 15,000,000.
CaptaiB. Meigs' orlglaal plan had to be modified 'several
times because of legal obstacles, but finally bids were opemed
Ik May, 18 58 for a riprap dam to extend from the hlaryland shore
to Conn's Island. The contract was awarded to Dexter Belknap of
New York on June 10,1858, The following was included in the
speolfioations:
1. The dam is to be an embankment of rubble stone with a
top width of SO ft., a slope on the upper side of one
to one, and on the lower side of five to one.
2. It will be made with large stones, the spaces filled with
smaller ones, so as to form a compact mass,
3. The eastern end of the dam (on the i-^ryland shore) will
be connected with the head wall of the feeder. The western
end will terminate against a ledge of rook.
The terms of the contract were as follows:
1. For clearing trees, brush, and logs from the
space flooded by the backwater of the dam
and occupied by the dam $ 50 per acre
2, For the rubble stone deposited in the dam,
including the cost of placing and packing
in conformity with the specifications $ 1,30 per ou.yd.
3, ?or broken stone , including the cost of the
stone, of breaking it, and depositing it in
the dam $ 1.00 pet cu.yd,
4, Gravelling, including cost of depositing in
the dam in accordance with the specifications 0.50 per ou.yd,
5. For excavation of rock in the boat channel
above the dam or under the site of the dam $ 1,00 per cu.yd,
6. For excavation of gravel, earth, and loose
stone in the boat channel above the dam or
under the site of the dam $ 0.15 per cu.yd.
This riprap dam was begun and built almost to the island.
Difficulties in obtaining land rights on Conn's Island prevented
Its completion.
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Om June 16, 186S Comgresa traasf erred the aqueduot from
the War Department to the Department of the iaterior. The
Secretary of the Interior put William H, Hut ton in charge of
the work and he was succeeded the following year by Silas
Seymour. Seymour inunediately expressed his disapproval of the
riprap dam and finally succeeded in submitting the question
of replacing it with a masonry dam to Congresa, On July S, 1864
Congress appropriated funds for the erection of a solid masonry
dam to extend from the Maryland shore to Conn's Island, The
contract was awarded to Dunbar, Sherrlll, and Bangs on July 30
and work was started Immediately. Great difficulty mas encount-
ered In obtaining laborers, owing to the high prices paid for
substitutes to enter the army and to the fear of incursions
from guerilla parties of Confederates, Considerable progress
was made In spite of delays caused by the CItII War and the
work was eompleted September 30, 1867, During actual construction
riprap diversions were used to fiirnish water, Exerpts from the
specifications follow:
1. Foimdation to rest on rock wherever practicable.
S, The masonry in the foundation Is to extend from the
rock foundation up to the level of low-water mark of
the river. The lower face will have a slope, either
in steps or batter, of two feet base to one foot rise,
and upper face in steps of one to one.
3. The lower or front face of the superstructure will be
vertical, the rear or downstream face will batter in
the ratio of four inches to the vertical foot,
4. The top of the dam will be 7 ft, thick and it is to
be of rubbla cement masonry,
5. The ooplng will be of Seneca sandstone.
6» The rear angle formed by the back face of the dam and
the bed of the river will be filled with good coarse
gravel or broken stone, extending from the top of the
daTO with a uniform slope not greater than 3 ft. horiz-
ontal to 1 ft, vertical until it reaches the bed of the
river.
.B-
The terms of the eo» tract were as follows:
For cleari»g & grubbing the entire work ^ 1800
For exoaTatiom i» foundations 2,50 per cu.yd.
For concrete & grout in foundations 6,00 per cu.yd.
For foundation nasonry 14,00 per cu.yd.
For superstructure masonry 14.00 per cu.yd.
For coping 20.00 per cu.yd,
J?'or wrought iron in bolts & olamps 0.15 per lb,
For back filling 3,50 per cu.yd.
The crest eleTatlon of this dam was 147,0 feet with mean low tide at
the Navy Yard in Washington as a datum. It was completed at a total
cost of ^ 50,000,
A rapid increase in the water consumption of the city of
Washington soon made it apparent that this solid masonry dam was
not high enough to Impoimd the necessary water to meet the new
requirements. In 1881 it was found that for 257 days of that year
the water at to eat Fills was below the leTel necessary for adeqiiately
supplying the District of Columbia, Temporary dans at the head of
Oonn'8 Island were built to meet the emergency but these, besides
being washed away each spring, did not meet the situation. The
problem was submitted to uongrese repeatedly and finally, on July
15,1862, an appropriation was made to finance the raising of the
existing dam to an eleration of 148. Q and to extend the whole
structure to the Virginia shore. The contract was awarded for this
work on Not ember 7,1883 to the Chittenden Bros. The old dam across
the Maryland channel was raised by putting a coping on it 15 inches
in thickness. The length of the old dam was 1034 feet. The extension
included a length of 669 feet across Conn's Island and 1174 feet
from Gonn*s Island to the Virginia shore. The new dam was to be a
masonry structure composed of large cut stone for the facing and
backing , with concrete filling, A flood which occurred the night
of October 29 and 30,1885 destroyed the coffer dams which had been
built and submerged the entire work. When the coffer dams were
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restored, it was fo-u»d that the flood had tora out from the dam
10-j^ ou.ydB, of eoaorete, 27f on, yds, of out stoae, aad 33^ ou.yde.
of eopiag which had Just beea put la place but act bolted. No
damage whaterer was doae to aay portloa of the completed dam im
which the mortar had had a ehaaoe to set. The damage was repaired
aad the work was fialshed oa August 31,1686 at a total cost of
$ 140,4B5.48, The completed dam had a total leagth of 2877 feet
amd raried ia height from 4 to SO feet, the deepest part belag
Im the Virgiaia chaaael. The width of the dam la the Marylaad
ohaamel was 7*- 9** while across Coaa's Islamd aad the Tirglala
chaaael it was 8'- 3**.
Ob Juae £,1889 a great flood occurred and the water rose to
a height of 16 feet above the crest of the dam. 1103 feet of eopiag
was washed off aad deposited ia the pool below. The damage was
repaired duriag the fayorable seasoas of 1890 aad 1891 at a cost
of $ 9000. The stoaes were replaced aad fasteaed with iroa bolts
fire feet loag aad two laches la diameter with heads oa them of
Buffioieat stremgth to preTeat the stoaes from sllppimg off.
Whea the dam had beea ezteaded to the Ylrgiaia side It was
thought that it would Impouad eaough water to supply the city of
Washiagtoa for all time. This was sooa fouad to be a mistake.
Prom 1886 to 1894 coasumptioa rose from 25,000,000 galloas per
day to 49,000,000 galloas per day while the populatioa lacr eased
oaly 30?&. The eleyatioa of the dam was partlcxilarly fouad to be
laadequate duriag low stages of the rirer. Oa Uareh 2,1895, a
sum of $ 185,000 was appropriated to raise the eleratloa of the
dam to 150.5 feet. This was doae by remoTiag the stoaes, iaoreasiag
the height, aad replaclag the eopiag. The ooplag was fasteaed
with bolts 2" ia diameter aad about 7' ia leagth. This work was
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eaupleted i« NoTember 1896 at a total cost of $ 101,373, This
was tlie last masomry corns true tiom dome om the dam. There has beem
mo serious damage slmce them, the omly repairs belmg replacememt
of the loose riprap baokimg which is partially carried away by
the ammiial sprlmg freshets.
After the hydro-electrlo plamt at Bale carl la was placed Im
serTicft im 1928, the Tclmae of water meeded was more tham doubled.
Flashboards of Douglas Fir were used to solve this problem. These
plamks are 12" high amd 2" thick. They are held im place by 2"
black Irom pipe stamdards set im holes drilled la the coplmg four
feet om cemter. The cost of this work which was completed im 1930
was $ 2,394.47. These flashboards brought the elevatiom of the dam
to 151.5 feet which is Its presemt elevatiom. Today the dam stamds
im perfect oomditiom with every imdieatiom that it still possesses
years of good service. The presemt value of the dan based om cost
of reproductlom is $ 450,000, A summary of the cost of the dam
follows:
Cost of lamd amd water rights $ 112,275.96
Cost of oomstruotlom 311,321.77
Total cost of aquisitlom $ 423,697.73
Source of fumds:
limited States I 289,168,87
District of Columbia 134.428.86
Total ¥ 423,697,73
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TYPlC^L SEICTION OF DAM AT GREAT FALLS
icaie
I" = 4-
WidtW o^ dam across Marylan4 CKani-iel -
WiclH\ across Conn's Is lamd K \/a. CKannel =
HeigM o-f do.rr' va»-ics ^vowvi -4^ ■" 2.0'
Average Wel^U-t ■= 15'
7'- 9"
Len9i"W of dann ■•
Across Marv^^Qnd Cho^v^^r^et
Across Conn's Islav^d
Acf'oss Vit-ginia CWannel
To4al Length
I0 34- f+.
Eleva + ioi^ of +op o-f -flavin- \ooards = 1 5 (. 5 fl. above
VTaeairt low -Vvdie. at tUe Wavv^ Yord \vi VV a^U vk^gt on ,\), C,
i^
/
Xhe new m^ake a^ Gre<\^ Fftl\s,Md.
^Tt.
A view o-f tlie ci
Owi
'^^^e ol<i i.^4ak(
i/
\ ; I
23
A pat-V o-f +tie Cc O CaM<
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WaTER-SEED of the POTOMAC AT GREAT FALLS, MARYLAND
The dral»age area of the Potomac RiTer at Ureat l?*all8
Is equal to 11,460 square niles*
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YEARIiY DISCHA.HGE OF THE POTOMAC HIYER AT GHSAT ?ALLS
soar
uazlnnn
MlKln^ra
M«am
1897
202,000
2300
13.700
1898
12S»000
1870
11,500
1699
132,000
1,790
15,500
1900
58,900
1,200
7,730
1901
169,000
1,150
14,300
1902
248,000
1,470
16,100
1903
123,000
1,840
17,300
1904
43,300
1,520
7.980
1905
76,500
1,070
8,270
1906
94,500
2,120
11.400
1907
131,000
2,970
16.600
1908
161,000
1,770
17.000
1909
82,400
1,440
7,750
1910
172,000
1,020
9,240
1911
119,000
828
7,690
1912
94,800
1,940
13.800
1913
143,000
848
9,500
1914
77,700
653
12,200
1915
141,000
775
11,800
1916
14R,000
1,310
12,400
1917
133,000
923
9,480
1918
126,000
1,060
11,200
1919
72.400
1.280
10.000
irg« for
t^® 248,000
653
11,900
All discharges
giv»M ia cuble ft.
per seooad.
Dralaage area of
the Potomac RiTor
at Great i<alls Is
11,460 eg.. mis.
The discharge of
the aqued-acts at
Great ^alls Is
seldom greater
tham 400 e.f.s.
23 year period
The above flgxires show that the average discharge of the Fotosiae
OTer a period of 23 years was 11,900 cable feet per seooad. Srea the
mialrn'oii of 653 c.f.s. is more thaa what is used by the aqueducts.
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Am iaterestimg report submitted by the U.S. Geological Survey
im 1913 reveals some decisive figures. The data follovs. All figtires
beyomd 1912 are estlinatds.
lear
Popnlatlom
Average Daily
Comsunptiom
Mazlmiim Dally
Com STimpt lorn
1906
323,000
68,700,000 (gallomsl
1906
326,000
67,400,000
1907
330,000
66,900,000
80.290,000 (gallons)
1908
339.000
64,910,000
80.380,000
1909
343,000
61,470,000
78,930.000
1910
343,000
54.190,000
78.600.000
1911
348,000
60.360,000
78.320,000
1912
354,000
62,120,000
92,720,000
1915
378,000
66,000.000
86,000.000
1920
406.000
70,000,000
91,000,000
1930
460,000
79,000,000
103,000,000
1940
515,000
89.000,000
116,000.000
1950
570,000
99,000,000
129,000,000
The discharge of the Potomac rtlver from fifteen years observation
varies froBi 600,000,000 to 84,000.000,000 gallons dally. As the
predicted maximum daily consumption in 1960 is only 129.000.000
gallons, it may be stated that the ir'otomac Hiver at Great Palls can
furnish for all time a sufficient water supply to the District of
Columbia.
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BIBLIOGRAPEY
AmBxial Reports of the tJ.S.Office of the Washimgtom Aqueduct
Com^esslo»al Reports om DeTelopmemt of Power at Great F&lls
Report of Major Tyler om Derelopmemt of Power at Great Slalls
Differ emt Issues of the SmglmeerlKg News
Imformatiom was also obtaimed from the Uaited States
Coast amd Geodetle SuTTey, the Umlted States Geological
SuTTey, the Corps of Emgimeera of the Umited States Army,
amd from people lirim^ mear the Great i^alls.
Corns ider able Imformatlom was obtaimed from Ur. Eardy
who Is Im charge of the Dale carl la Reserrolr amd flltratiom
plamt amd who also has dome mueh work om the dam,
I am Indebted also to Mr, Moffeems,who is im charge of
the McMillam Park Reservoir im washimgtom, for much imformatiom.